As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FAILURE IN THE BACKUP ELECTRICAL SYSTEM HAS OCCURRED THAT CANNOT BE ATTRIBUTED TO A BACKUP GENERATOR. STATUS MESSAGE 2448070 LATCHED AP MODE MESSAGE 2448070 LATCHED AP MODE. FOUND STATUS MESSAGE 'ELEC BACKUP SYS' DISPLAYED WITH CORRELATED MAINT MESSAGE 2448070. REPLACED BUG CONVERTER & CONTACTOR (TBB), GRD RUN WITH CREW, CHECKED BOTH IDG AND BUG SYSTEM FUNCTIONALLY OK.